1. Field of the Invention
The present invention relates generally to a fiber mat and a process of making the same. In particular, the present invention relates to a glass fiber mat comprising fibers, a binder and a binder modifier. Embodiments of the present invention can have desired characteristics, such as, for example, improved wet web strength and dry mat tensile strengths as compared with a conventional mat where no modifier is employed, and can be suitable for use in building materials.
2. Description of the Prior Art
High strength fiber mats have become increasingly popular in the building materials industry. Most commonly used in roofing shingles, fiber mats have numerous other material applications, including use in roofing, siding and floor underlayment; insulation facers; floor and ceiling tile; and vehicle parts.
Various fiber mats and methods of making the same have been previously described. For example, U.S. Pat. Nos. 4,135,029; 4,258,098; 5,914,365; and 6,642,299 describe glass fiber mats made by a wet-laid process. Glass fiber mats made by the wet-laid process are formed from glass fibers held together by a binder material. The last two patents relate to improved wet web strength with styrene-maleic anhydride copolymer (SMA), styrene-acrylate copolymers, and mixtures thereof.
Typically, in wet processed glass fiber mats, the binder is applied in a liquid form and dispersed onto the glass fibers by a curtain type applicator. Conventional wet processes strive to produce a uniform coating of binder on the glass fibers. After the binder and glass fibers have been dried and cured, the glass fiber mat is cut as desired.
A major problem in the manufacturing process and use of some known fiber mats is inadequate wet web strength. The wet web strength of wet glass mat has significant impact on runnability of glass mat production and mat properties. In order to prevent mat web from breaking during production, the production line speed has to be reduced due to a lower wet web strength of wet glass mat before curing. Also, a lower wet web strength requires a higher vacuum drawing to support the wet web and minimize web breaking. But the higher vacuum drawing will lead to undesired mat property, such as a high mat tensile ratio.
Inadequate dry mat tensile strengths also can reduce the ability of the finished roofing product to resist stresses during service on the roof. Because building materials, generally, and roofing shingles, in particular, are often subjected to a variety of weather conditions, the fiber mats should also maintain their strength characteristics under a wide range of conventional conditions.